This invention relates to systems which employ water as a heat exchange medium so as to add or remove heat from various parts of a building that are to be heated or cooled.
It is desirable that a system for heating or cooling various parts of a building be capable of responding to different demands for heating or cooling throughout the building at any time of the day or night. It is moreover desirable that such a system be capable of responding to reduced demands for heating or cooling during evening or nighttime hours when various parts of the building may not be occupied. It is also desirable that these same parts of the building be brought up or down to comfortable temperature levels during occupancy. This need to meet comfort levels during occupancy can present particular problems in a system using water as the preferred heat exchange medium in adding or extracting heat from the various parts of a building. In this regard, water in such a system may need to be first heated or cooled by appropriate equipment and thereafter circulated in advance of occupancy in order to meet the desired comfort levels during occupancy. This need to first heat or cool the water poses particular problems when the system must transition from providing temperature conditioned water of a first type to providing temperature conditioned water of a second type.
It is an object of the invention to provide a control for a system employing water as a heat exchange medium which will provide either heated or cooled water to parts of a building in advance of occupancy.
The present invention includes a controller for a system providing conditioned water to preferably a number of individual heat exchangers. The controller gathers information from local dedicated controllers for each of the heat exchangers. The gathered information includes the current heating or cooling demand by each such local controller as well as the current zone temperature for the space to be heated or cooled by the local heat exchanger. The gathered information furthermore includes the next future setpoint for the zone and associated start time for the future setpoint.
The controller preferably creates an array of the thus received information by zone. The controller furthermore uses the received information that has been organized by zone to compute several additional pieces of information for each particular zone that is preferably stored in additional fields within the array. The additional pieces of information include time required to achieve a heat setpoint for the particular zone, time required to achieve a cool setpoint for the particular zone, a heat start time and a cool start time.
The controller preferably first computes the percentage of dedicated local controllers currently having heating demands and the percentage of zone controllers currently having cooling demands. The controller next determines whether the computed percentage heating requirement is greater than the percentage cooling requirement. In the event that the percentage heating requirement is greater than the percentage cooling requirement, then the controller preferably inquires as to whether the particularly dominant heating requirement is greater than a minimum heating demand requirement. In the event that the percentage cooling requirement is greater than the percentage heating requirement, then the controller inquires as to whether the particularly dominant cooling requirement is greater than a minimum cooling requirement.
In the event that the dominant percent heating or cooling requirement is not greater than the respective minimum demand level, than the processor will proceed to an advance start routine. The advance start routine will determine whether or not there are anticipated demands in the future that might be sufficient to produce a future heating or cooling requirement that would be greater than the respective minimum level of demand. If a future heating or cooling requirement is greater than its respective minimum requirement, then the controller will proceed to determine the earliest start time that would produce a future heating or cooling requirement that just exceeds the respective minimum demand level.
The setting of a system demand either equal to heating or equal to cooling either by virtue of the original comparison of present heating or cooling demands with respect to minimum requirements or the computed future heating and cooling demands with respect to the minimum requirements may not however result in the immediate provision of the conditioned water being demanded. The system will first check to see whether the currently active heating or cooling equipment has run for a minimum time period if there is to be a change over to the other type of equipment. When this minimum time period has expired and the particular active equipment has been stopped, the control will preferably inquire as to whether a particular water temperature in the return line is within a range of temperatures. The system may also inquire as to whether a particular period of time has elapsed since the previous activated equipment was turned off. It is only after the return water temperature is within range or the period of time since turning off the previously activated equipment has elapsed, if the later has occurred, that the controller will proceed to actually authorize the start up of the particular heating or cooling equipment pursuant to the setting of the system demand in accordance with the aforementioned computation of either present or future demand requirements for either heating or cooling.